Bourbon is a multi-billion dollar market, but American barrel-aged whiskey also produces a lot of wasted grain at the distillery. Chemists at the University of Kentucky developed a method to turn that stillage into electrodes and used those electrodes to create supercapacitors with energy storage capacities comparable to existing commercial devices. He presented his work at a meeting of the American Chemical Society in Atlanta, Georgia.
American distillers began making bourbon in the 18th century, particularly in Kentucky, but it really took off commercially in terms of consumption and export after World War II. Legally, a whiskey can be sold as bourbon only if its mash contains at least 51 percent corn and the remainder any other grain (usually rye and barley).
The grain is ground and mixed with water, and mash from the previous distillation is added to create a sour mash. The addition of yeast begins fermentation, after which the mash is distilled into a clear spirit called “white dog”. That spirit is then poured into charred new oak barrels to age for at least two years. It is the caramelized sugars and vanillin in the burnt wood that give bourbon its distinctive dark color and flavor. The barrels for bourbon are never reused, usually recycled to make barrel-aged beers, wines, and even barbecue and hot sauces.
While the barrels are recycled, much of the watery used mash (stillage) is wasted. Josile Barrios Cosio, a graduate student in chemistry at the University of Kentucky, was shocked to learn that for every last barrel of bourbon produced, there are six to 10 times as many barrels wasted. It is often sold to farmers as animal feed or soil additive, but it is expensive to dry and difficult to transport when wet. Barrios Cosío and his PI, Marcelo Guzmán, thought it might be possible to convert the watery consistency into useful carbon material using a high-intensity pressure cooking technique called hydrothermal carbonization.
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